Ask Josh Anything #003

Thanks for answering this one on the podcast. Much appreciated. Great show, enjoying every episode. I know some people said they don’t like the music you use on the show, but I think it’s great!

Hi Josh,

in a rare occurrence, I’m going to disagree with you. Well, more specifically, I’m going to disagree with your methodology. You said, “That 10T cog really shouldn’t exist,” but in making that argument you focus solely on the frictional aspects of chain articulation in comparing an 11T vs 10T cog. But this leaves out a (potentially) significant consideration – aerodynamics. When considering 1X vs 2X drivetrains, any discussion that neglects the frontal area savings of removing front derailleur & derailleur hanger is incomplete. But frontal area also plays a role when considering chainring and cassette sizing for 1X drivetrains.

We know that the drag on a flat plate is not insignificant. Comparing a 50T x 10/28 drivetrain vs a 54T x 11/32 drivetrain, the frontal area differences between the 50T vs 54T chainrings should be considered. And even the frontal area differences between a 10/28 cassette and an 11/32 cassette are relevant, especially on a disc wheel where any additional FA “replaces” the “clean” surface of the disc. This is because the 10T is, inherently, a “high speed” cog. A rider in 50-10 is going at speeds where 90%+ of the resistance is aerodynamic, so it doesn’t take much of a FA difference to overcome the frictional losses.

There’s also the potential jump in FA from needing to make the shift from a short—>medium or medium—>long cage rear derailleur. These bumps in FA area all marginal, but they can add up, especially at high speed.

If 10T doesn’t have a place, it’s likely in gravel-type situations where speeds are lower and the difference between a 40-10 and a 44-11 is even greater because of the greater deflection on the chainring as well as the cog. But on the road side, with higher speeds, even marginal differences in FA can be potentially significant, and dismissing the 10T without acknowledging the reduced FA of a drivetrain with a 10T cog seems reflective on an incomplete analysis.

The 10T cog may still lose out at the end of the day. But in making that statement without considering the FA of the drivetrain, I think you’re leaving some important details out.

All the best,

Jordan

Hi Guy’s

Love the podcast.

I have a question regarding rim depth I do Time Trials in what is called a Merckx/Road class. You’re not allowed to have aero parts you ride a straight up, road bike. This year they changed the rule for wheels from 32mm to 38mm deep rims. Currently, I am using Shimano Dura Ace C24 21mm front and 24mm in the rear. So I know we’re talking marginal gains but how much performance gains could one except say going to a rim in the 35mm to 38mm range. I know you can save big time in a 40k TT with deep rims, I am only doing 16k TT’s and it’s all flat. Rims are not cheap so would I be better spending my money on fast tires, latex tubs, skin suit (they will let you use them), an aero road helmet. I never had deep rims I know with the 40mm + you can hold speeds over 25mph easier but with the shallow depth, rims they must top out at some point.

Thanks again for the work you put into the podcast

Regards,

Dave

This might be my new favourite podcast. Awesome!

2 questions.

1) Aero over weight.

Using best bike split, this looks very clear. But when you add in the extra element of riding in a 50 rider size bunch on the flat…..are the aero gains of an more aero, but heavier wheelset or frame mitigated to the point where weight starts to matter more when you have a main climb in the race or course? Assuming you never take a turn on the front of the peloton. Does this explain why marquee climbers still stick with light bikes over aero bikes in the pro tour?

2) If you have aero data on a wheel, tested in a tunnel, presumably on it’s own or as the front wheel, what is the general consensus of the type of aero performance reduction would you expect for the back wheel (behind a frame, churning legs and crank etc)? All companies would post aero data of a front wheel hitting the clean air, so you wouldn’t just double that for 2 wheels, or would you? Or does it vary so wildly that there’s not a typical range?

Thanks for the shows! Love them.

Hi guys. Love the show. I have a question for Josh about ceramic bearings. I’m very curious – not about how fast they are compared to steel bearings – but rather how they are made and what they are made of. I can’t see the similarity between ceramic bearings and ceramic plates, cups, tiles, sinks and toilets. Do ceramic bearings have any relationship to other “ceramic” items, or none at all? If so, how are they so strong when everything else made of ceramic is incredibly easy to shatter? I realise that’s a few questions rolled into one but I would love it if Josh could explain this to me and other listeners. Keep up the great work.

All the best from Santiago, Chile!